A plasma processing apparatus is used in manufacturing semiconductor devices. The plasma processing apparatus performs an etching process, a chemical vapor deposition (CVD) process, and the like on a semiconductor wafer, by using plasma. The plasma processing apparatus generates the plasma in a processing chamber while a semiconductor wafer is mounted on a substrate mounting table disposed in the processing chamber. Then, a predetermined plasma process is performed on a surface of the wafer by the plasma.
Depending on plasma sources for generating the plasma, plasma processing methods or apparatuses are classified as capacitively coupled plasma (CCP), electron cyclotron resonance plasma (ECRP), helicon wave plasma (HWP), inductively coupled plasma (ICP), and microwave excitation surface wave plasma (SWP). In the plasma sources except for the CCP, a discharge power and a bias power are independently controllable. Therefore, these plasma sources are used to make the control of an etching shape and the like easy.
In a semiconductor manufacturing process, a plasma processing apparatus is employed as an apparatus included in, for example, a metal film forming system. Patent References 1 and 2 disclose a metal film forming system 100 in which a plasma processing apparatus is included as a pre-cleaning device 115 for a semiconductor wafer, as illustrated in FIG. 9. The metal film forming system 100 includes a transfer chamber 110, a transfer arm 119, and a group of devices 111, 112, 113, 114, 115, 116, 117 and 118 disposed around the transfer chamber 110. The group of devices includes cassette chambers 111 and 112, a degassing chamber 113, a titanium (Ti) film forming device 114, a pre-cleaning device 115, a titanium nitride (TiN) film forming device 116, an aluminum (Al) film forming device 117, and a cooling chamber 118.
The metal film forming system 100 is used for forming a barrier layer on a semiconductor wafer in which a contact hole and/or a via hole are formed and forming a metal layer (Al wiring) by burying Al within the hole on the barrier layer thus formed. Specifically, the transfer arm 119 takes out one sheet of a semiconductor wafer from the cassette chamber 111 and tranfers the semiconductor wafer into the pre-cleaning device 115 so that a native oxide film on a surface of the semiconductor wafer is removed by plasma etching.
Subsequently, the transfer arm 119 transfers the semiconductor wafer into the degassing chamber 113 so that a degassing process is performed on the semiconductor wafer. Subsequently, the transfer arm 119 transfers the semiconductor wafer into the Ti film forming device 114 so as to form a Ti film and then transfers it into the TiN film forming device 116 so as to form a TiN film as a barrier layer. Further, the Al wiring is formed on the semiconductor wafer by the Al film forming device 117. Finally, the semiconductor wafer is cooled in the cooling chamber 118 and is transferred into the cassette chamber 112.
Accordingly, the barrier layer and the metal layer (Al wiring) which is formed on the barrier layer and is conducted to an impurity diffusion region are formed on, for example, the semiconductor wafer in which the contact hole if formed, wherein the contact hole passes through an interlayer insulating film to the impurity diffusion region.
In semiconductor manufacturing, a plasma processing apparatus is used as a plasma etching apparatus as well as a plasma CVD apparatus. A film formed by the CVD of the plasma CVD has an improved step coverage, compared to a film formed by sputtering. Therefore, the CVD is more favorable than the sputtering, when a barrier layer is needed to be formed inside the contact hole, the via hole and the like, for example, for the case of the metal film forming system 100.
However, in the CVD, a material of a film needs to be vaporized to be supplied into a chamber. A vaporizing device of the material of a film is one of the factors for preventing a reduction in a manufacturing cost in a CVD apparatus. Further, in the CVD, a vaporable material of a film needs to be used. Therefore, in the CVD, available materials for a film are limited. This limitation can be a factor increasing the manufacturing cost since high price materials may have to be used in the manufacturing process, depending on a kind of films to be formed. For example, iridium (Ir) is used as a material in an electrode film of lead zirconate titanate (PZT) which is noticed as a material for ferroelectric RAM. However, the materials for forming an Ir film by metal organic CVD (MOCVD) is very expensive.    [Patent Reference 1] Japanese Patent Laid-open Application No. 2002-237486    [Patent Reference 2] Japanese Patent Laid-open Application No. 2003-124201